The current goals are to study the distribution, specificity, biogenesis, and possible physiological significance of anionic sites on normal and malignant baby hamster kidney cells; to determine the uptake, binding and distribution of LDL receptors on human fibroblast surface membranes; to study the cell surfaces of human lymphocytes by analysis with specific antisera directed against B and T cell components; to study the influence of cyclic AMP on gap junction assembly and the role of microfilaments and microtubules in the development of formation plaques and differentiation of the junctions; to study surface microextensions of cells, their formation, response to physiological stimuli, and possible physiological significance; and to study the nature of the junctional complexes which form between cultured cells.